Aeration device

ABSTRACT

An aeration device comprising a rotating disc having porous surfaces through which a fluid can be passed to be dispersed into a liquid in which the disc is rotating.

United States Patent Werner [45;] Mar.21, 1972 AERATION DEVICE [72]Inventor: Frank D. Werner, 5405 Mt. Normandale Curve, Minneapolis, Minn.55431 [22] Filed: Apr. 4, 1969 [21] App]. No.: 813,466

[52] US. Cl ..261/87 [51] Int. Cl. ..B0117/26 [58] Field of Search..261/87,93, 122

[56] References Cited UNITED STATES PATENTS 1,124,855 1/1915 Callow etal. ..261/87 1,285,494 11/1918 Wallace et al. ..261/122 1,374,446 4/ l921 Greenawalt ..261/87 2,121,458 6/1938 Vogelbusch. ..261/87 X2,944,802 7/1960 Daman... ..261/93 X 2,996,287 8/1961 Audran. ...261/87X 3,256,802 6/1966 Karr ..261/122 3,464,552 9/1969 Warman ..261/87 X3,490,996 1/1970 Kelly, Jr ..261/87 Primary Examiner-Tim R. MilesAssistant ExaminerSteven H. Markowitz Attorney-Bugger, Peterson, Johnson& Westman ABSTRACT An aeration device comprising a rotating disc havingporous surfaces through which a fluid can be passed to be dispersed intoa liquid in which the disc is rotating.

14 Claims, 8 Drawing Figures Patented March 21, 1972 2 Shoots'Shoot lFIE: 5

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INVEN'I'OR. FRANK .D. 14/549052 BY ?M Patented March 21, 19 72 3,650,513

2 Sheats-Sheet 2 AERATION DEVICE BACKGROUND OF THE INVENTION l. Field ofthe Invention The present invention relates to devices for dispersing afluid into a liquid.

2. Prior art Various aeration devices have been advanced wherein a gascan be dispersed into a liquid with a rotating elementsRotating discshave been shown in U.S. Pat. No. 1,242,445, US. Pat. No. 1,374,446, U.S.Pat. No. 2,996,487 and others. These patents all show large orifices inthe discs for thegas. Some have substantially the entire peripheraledgeportion of the disc open. In addition to the rotating disc types ofaerators there are many that use a rotating propeller or vane whichcauses a good deal of turbulence. The'turbulence of course results inincreased horsepower requirements and the desired effect of havingminute bubbles dispersed into the liquid is not efficiently achieved.

SUMMARY OF THE INVENTION The present invention has relation to arotatingdisc like element for mixing a fluid into a liquid in which the disc isrotating. The disc is made so that it does not cause any excessiveturbulence or disturbance to the liquid as it rotates. The disc hasporous surfaces with minute openings through which a fluid (gaseous or aliquid) is released as the disc rotates. These porous surfaces are madeup of a sintered metal or similar material having minute pores oropenings.

The use of a vibration causing device which helps to displace the smallbubbles from the rotating disc is alsodisclosed. The invention alsocomprises introducing humid or nearly saturated air or gas into theliquid to prevent evaporationof water right at the porous surface.Evaporation of the liquid particularly water, can cause carbonates orother solutes to collect on the porous surface thereby plugging up theorifices through which the gaseous fluid is dispersed into the liquid.

Utilizing a disc means that physical displacement of the water isminimized as the disc rotates, and the fluid is swept off the poroussurfaces in minute bubbles and is carried outwardly without turbulencecaused by liquid displacement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevationalview ofa device made according to the present invention installed withina tank in which aeration ofa liquid is to takeplace;

FIG. 2 is a sectional view taken as on line 22 in FIG. 1-,

FIG. 3 is a sectional view taken as on line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken as on line 4-4 in FIG. 3;

FIG. 5 is a sectional view taken on substantiallythe same line as FIG. 4showing anoptional configuration for the outer ends ofthe rotating disc;

FIG. 6 is a top plan view of the deviceof FIG. 4 showing vibrating rodsinstalled to cause vibration of the disc as it rotates;

FIG. 7 is a top plan view of a further modified form of the presentinvention; and

FIGHB is a sectional view taken as on line 8-8 in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG.1 shows schematically a tank in which a liquid, such as water 11 iscontained, and which is to be aerated. The term aeration as used hereinmeans that a liquid is to have a gaseous fluid dispersed therein.Normally this is an introduction of air which is necessary for aerationof sewageor the like. The term is to include the dispersion of any fluidwithin another fluid or liquid by the structure ofthe devices disclosed.

The tank supports a platform or frame .12 on which a drive motor 13 ismounted. The motor can be ,powered to rotate a hollow shaft 14. Asshown, the hollow shaft 14 extends through the motor, and the shaft isopen to a conduit 15 leading from a source 16 of suitable fluid whichcan be under pressure or not depending on the requirements. A fluidcarrying rotating joint coupling 15A connects the conduit 15 to shaft14. The fluid can be air, oxygen, or any other fluid, preferablygaseous, that is to be dispersed into the liquid 11.

The shaft 14 has a hollow disc-like assembly 17 at its lower end, which,as shown, comprises two dishedmembers 20 and 21 joined together at anouter edge portion 22 which is tapered and comes out to a relativelysharp peripheral edge. The disclike member is therefore generallylenticular (double convex) in shape. As shown, the disc-like memberitselfis hollow between the planar members 20 and 21, and the fluid orgas coming from the source 16 through the conduit 15 is fed through theinterior passageway of the shaft 14 and into the interior chamber 24ofthe disc.

Adjacent the peripheral edges of the disc, but not out at the edgeportions 22, there are sections of the members 20 and 21 which are madeup of a material having minute pores therethrough. These sections areshown at 25 in FIGS. 2, 3 and 4 in this form of the invention. Thesesections of material can be completely annular if desired, or can bemade up into segments as shown. The material is made to have a multitudeof very fine pores, desirably ranging from about 5 to 50 microns in meantransverse dimension, such as sintered metal, ceramic or finely porousplastic which will permit small bubbles of the gaseous material comingfrom chamber 24 to pass through the walls or portions 25 and form on theouter surfaces of the disc. The porous material is of substantiallyuniform density throughout the wall thickness. Thus when the disc isrotating in the liquid 11, the disc can achieve a high velocity, and thesmall bubbles forming on the surfaces 25 will be swept off by the liquidmoving past the surfaces. The centrifugal flow of the boundary layer ofwater moving radially outwardly along the disc will carry "these sweptoff bubbles outwardly into a stream of bubbles illustrated generally at26 and these small bubbles will disperse throughout the liquid, causingoxygen to be dispersed. One of the points of interest here is that thereis no excessive turbulence because the disc itselfdoes not displace anywater as it rotates. It is symmetrical about its rotating axis so thatthere is no turbulence created except within the boundary layer, whichmay be either laminar or turbulent, depending on the Reynoldss Number,in a well known way. There is a thin boundary layer of water that moveswith significant speeds and this boundary layer will move outwardlycausing the bubbles to be swept off and dispersed into the liquid.

In FIG. 5, the wall members 20 and 21 are terminated inwardly from theouter edge of the assembly. The outer edge portion here comprises acomplete annular section 30 including an outer peripheral member 31, andannular outwardly raised convex portions 32 between the members 20 and21 and the peripheral member 30. The enlarged portions look much likeairfoils in cross section as shown in FIG. 5, and the finely porous wallportions 33 are placed inthese airfoil portions. The gas coming inthrough the hollow disc will be dispersed out throughthe porous wallportions 33. Because of the radial water flow over the convexairfoil-like portions 32, and well known physical principles, the porousportions 33 may be at a much lowerpressure on their outer surface thanthe surrounding portions. If the pressure drops enough, the devicemaybecome self pumping so that the reduction in pressure will actuallycause the gas to pass through the porous material 33, forming bubbles onthe outer surfaces thereof. The radial sweep of the water as it passesoverthe airfoil-like portions causes this self pumping action. This alsoaids in reducing the horse-power required for operation of the unit. Ina selfpumping situation there would not be any need for a sealedrotating joint such as that shown at 15A which is necessary if a conduitis used and fluid under pressure is supplied by the source 16. Therotating shaft 14 could be merely open to the atmosphere and the selfpumping action could take care of the pumping of air into the liquid.

in FIG. 6, a modified form of the invention is shown. This device is thesame type of disc as that shown in FIG. 3, and has the porous portion 25on the disc 17. However, short radial rods 37 are provided at theperiphery. These rods will vibrate as the disc rotates causing thebubbles forming on the surfaces of pads 25 to be vibrated off as thedisc rotates thus increasing the dispersion of the bubbles into theliquid. The rods need not be circular in cross section, and the rodswill respond by giving a frequency of vibration that is dependent upontheir shape, length, and velocity. This effect is well known in fluiddynamics, one popularly known result being a singing or gallopingelectrical line when wind blows across it. in the present case, thehollow shaft acts as a torsional spring and the disc as a flywheel,undergoing torsional vibrations.

In a vibrating disc, if a small bubble is about to be washed off theporous surfaces 25, and the disc has torsional oscillation or vibrationcaused by the rods 37, the bubble will experience maximum velocity peaksto wash it off without any increase in average velocity. In other words,the velocity of the bubble will increase and decrease from thevibrations, but the average velocity would not change. Since the averagevelocity governs power consumption, this would mean that more bubblescould be shaken off with the same power being consumed. The more bubblesthat are shaken off with the same power consumption means that a greaterdispersion of oxygen into the liquid 11 is achieved without increasinghorsepower consumption.

In FIGS. 7 and 8, there is a further modified form of the invention.Here, the disc-like member 40 is again mounted onto the hollow shaft 14.There are peripheral porous pad members 41 made up of a sintered metalmaterial or the like as in the previous forms of the invention and theseare positioned right at the peripheral edge of the disc-like member 40.The porous portion could be positioned at the top and bottom surfaces aswell.

In the top and bottom of the disc member 40, which again has a hollowinterior, tapered vanes 42 are provided which extend radially outwardlyfrom the shaft 14 or from the center of the disc on the bottom part.These vanes thus cause a flow of water radially outwardly as the unitrotates. The disc gives greater turbulence, but also gives larger waterflow as well. This causes a pumping and physical displacement of thewater so that the bubbles at the porous surfaces of the disc will beswept off both by the radially outward pumping caused by the vanes 42and also by the sweeping by of the water as the disc rotates. Thesevanes or blades need not be of the refined shape described. Simple,non-tapered ribs will serve to increase the radial pumping, if theirsimpler shapes are preferred. If desired, they need not extend all theway inward to the shaft, nor outward to the periphery.

Again, getting many many small bubbles into the water is the primeobjective and this is accomplished with the radial pumping action.

The sintered metal can be of any desired porosity. The pores areextremely small, desirably in the range of to 50 microns, so thatbubbles in the range of 5 to microns in diameter are collected on thesurface of the porous material and are swept off by the water as itflows outwardly. The small bubbles have a large proportionate surfacearea for the volume of gas being dispersed into the liquid and thisgreatly aids in the absorption of the gas in the liquid.

In all forms of the invention, the source of fluid 16 can be made tosupply a humid air or gaseous fluid so that it is preferably fullysaturated with water vapor as it passes through the hollow shaft 14 andout through the pores of the porous pads 25, 33 or 41. The fullysaturated air thus insures that as it enters the liquid there will be noevaporation of the water right at the orifices. This evaporation ofwater at the orifices of aeration devices causes a build up ofcarbonates and other foreign material that will precipitate out when thewater evaporates. The precipitates cause a clogging of the pores in thematerial through which the gas passes. When extra fine pores are used,such as those in the present invention, this becomes more of a problem.By using a fully saturated fluid from the source of fluid 16 (fullysaturated with water vapor), this clogging up of the pores clue to thecollection of carbonates and other foreign materials caused byevaporation of the water in which the gas is being dispersed on theporous pads is greatly reduced, and is substantially eliminated.

The rotating members as shown are of uniform radial cross section aroundthe axis of rotation to make sure there is no water displacement andresulting turbulence from the discs themselves as they rotate.

The present device is also useful for dispersing drops or globules ofafirst liquid into another liquid with which the first liquid isimmiscible. The source of fluid 16 would be a source of the first liquidand the second liquid would be in container 10. The sintered metalsections on the rotating disc would provide small droplets of the firstliquid on the surface of the disc which would be swept off and dispersedin the second liquid just like the bubbles described.

Iclaim:

1. In a device for dispersing a fluid into a liquid, a disc like member,means to mount said disc like member for rotation about an axis in saidliquid, said disc like member having first and second spaced wallsextending outwardly from the axis of rotation, and having asubstantially identical cross sectional shape annularly about said axisof rotation, said walls being spaced apart on the main portion of saidmember and tapering together to form a narrow edge portion at theperiphery of said disc like member, said spaced walls forming anunobstructed interior chamber which narrows adjacent its peripheraledges, a source of fluid, a conduit open from said source of fluid tosaid chamber, and means on said disc like member comprising a porouswall portion spaced from the peripheral edge having openings throughwhich said fluid may pass from the interior of said disc like member tosaid liquid.

2. The device of claim 1 wherein said wall portion comprises at leastportions of the exposed surface of said disclike member, and comprises asintered metal material.

3. The device of claim 1 wherein said porous wall portion is only on theupper and lower surfaces of said disclike member, the outer peripheralportion of said disclike member being ofa non porous material.

4. The device of claim 3 wherein said porous wall portion is positionedbetween the axis of rotation of the disclike member and the outerperipheral portions, and has at least one surface that is substantiallyairfoil shaped in radial cross section to cause a reduction of pressureat the surface of said disclike member from liquid moving outwardly fromthe axis of rotation of said disclike member as the liquid passes oversaid porous wall portion.

5. The device of claim 1 and a plurality of substantially radiallyextending vanes on the outside of said disclike member.

6. The device of claim 1 wherein said disclike member has porous wallportions at both the top and bottom thereof.

7. The combination as specified in claim 6 wherein the wall portions onboth the top and bottom walls of said disc have convex radial crosssections between the axis of rotation and the outer peripheral portionsof the disclike member.

8. The device of claim 1 wherein said source of fluid comprises a sourceof gas that is substantially saturated with vapor of the samecomposition and at the same temperature as the liquid into which the gasis introduced through said disclike member.

9. The device of claim 1 and a plurality of radially extending rodmembers spaced apart around the peripheral edge of said rotating discand fixedly attached to said rotating disc.

10. In a device for dispersing a fluid into a liquid, a generallylenticularly shaped member, means to mount said member for rotationabout an axis centrally located on said member and extending atsubstantially right angles to the general plane of the member in saidliquid, said member defining an unobstructed interior chamber, a sourceof fluid, a conduit open from a source of fluid to said interiorchamber, and means forming a part of said member comprising a wallportion having openings open to the outer surface of the member spacedfrom the peripheral edge of said member and in communication with theinterior chamber so that fluid may pass through the openings in saidwall portion from the interior chamber of said member to said liquid.

11. The device of claim wherein said wall portion comprises finelyporous material having pores varying between 5 and 50 microns in meantransverse dimension.

12. The device of claim 1 wherein said porous wall portion is positionedbetween the axis of rotation of said member and the outer peripheralportions, and said porous wall portion has at least one surface that isconvex in radial cross section between the axis of rotation and theperiphery to cause a reduction of pressure at the outer surface of saidmember from liquid moving outwardly from the axis of rotation of saidmember as it passes over said porous wall portion.

13. The device of claim 1 wherein said fluid comprises a second liquidthat is immiscible in the first mentioned liquid.

14. The device of claim 1 and means for inducing torsional vibration ofsaid disc like member about its axis as said disc like member rotates.

1. In a device for dispersing a fluid into a liquid, a disc like member,means to mount said disc like member for rotation about an axis in saidliquid, said disc like member having first and second spaced wallsextending outwardly from the axis of rotation, and having asubstantially identical cross sectional shape annularly about said axisof rotation, said walls being spaced apart on the main portion of saidmember and tapering together to form a narrow edge portion at theperiphery of said disc like member, said spaced walls forming anunobstructed interior chamber which narrows adjacent its peripheraledges, a source of fluid, a conduit open from said source of fluid tosaid chamber, and means on said disc like member comprising a porouswall portion spaced from the peripheral edge having openings throughwhich said fluid may pass from the interior of said disc like member tosaid liquid.
 2. The device of claim 1 wherein said wall portioncomprises at least portions of the exposed surface of said disclikemember, and comprises a sintered metal material.
 3. The device of claim1 wherein said porous wall portion is only on the upper and lowersurfaces of said disclike member, the outer peripheral portion of saiddisclike member being of a non porous material.
 4. The device of claim 3wherein said porous wall portion is positioned between the axis ofrotation of the disclike member and the outer peripheral portions, andhas at least one surface that is substantially airfoil shaped in radialcross section to cause a reduction of pressure at the surface of saiddisclike member from liquid moving outwardly from the axis of rotationof said disclike membeR as the liquid passes over said porous wallportion.
 5. The device of claim 1 and a plurality of substantiallyradially extending vanes on the outside of said disclike member.
 6. Thedevice of claim 1 wherein said disclike member has porous wall portionsat both the top and bottom thereof.
 7. The combination as specified inclaim 6 wherein the wall portions on both the top and bottom walls ofsaid disc have convex radial cross sections between the axis of rotationand the outer peripheral portions of the disclike member.
 8. The deviceof claim 1 wherein said source of fluid comprises a source of gas thatis substantially saturated with vapor of the same composition and at thesame temperature as the liquid into which the gas is introduced throughsaid disclike member.
 9. The device of claim 1 and a plurality ofradially extending rod members spaced apart around the peripheral edgeof said rotating disc and fixedly attached to said rotating disc.
 10. Ina device for dispersing a fluid into a liquid, a generally lenticularlyshaped member, means to mount said member for rotation about an axiscentrally located on said member and extending at substantially rightangles to the general plane of the member in said liquid, said memberdefining an unobstructed interior chamber, a source of fluid, a conduitopen from a source of fluid to said interior chamber, and means forminga part of said member comprising a wall portion having openings open tothe outer surface of the member spaced from the peripheral edge of saidmember and in communication with the interior chamber so that fluid maypass through the openings in said wall portion from the interior chamberof said member to said liquid.
 11. The device of claim 10 wherein saidwall portion comprises finely porous material having pores varyingbetween 5 and 50 microns in mean transverse dimension.
 12. The device ofclaim 1 wherein said porous wall portion is positioned between the axisof rotation of said member and the outer peripheral portions, and saidporous wall portion has at least one surface that is convex in radialcross section between the axis of rotation and the periphery to cause areduction of pressure at the outer surface of said member from liquidmoving outwardly from the axis of rotation of said member as it passesover said porous wall portion.
 13. The device of claim 1 wherein saidfluid comprises a second liquid that is immiscible in the firstmentioned liquid.
 14. The device of claim 1 and means for inducingtorsional vibration of said disc like member about its axis as said disclike member rotates.